Machine for bending sheet stock

ABSTRACT

A machine for bending metal sheet or plate stock into a blank of U-shaped cross section, having a plurality of frames which are closed at the top and are disposed along a line in relation to which the stock is to be bent, each frame comprising an upper frame and a lower frame, there being sheet bending members in the lower frame and hydraulic press means with bending punch; each of said upper frames having a pair of tension and tie bar members, hinged individually with their respective lower ends to the lower frame and being inclined towards each other for positions of their upper ends in close proximity to each other; each upper frame further including a horizontally extending cross tie hinged to the said bars close to but not at their said upper ends, the hydraulic means including a press cylinder, being mounted to said cross tie; and resiliently yielding hinge means at the said upper ends of said bar members for interconnecting bar members and hingedly connecting them to each other. The hinge means comprising a pair of bearing segments respectively connected to the upper ends of the bar members, a cylindrical hinge pin engaged by the segments; and tie rod means for resiliently urging the segments into engagement with the pin but permitting partial disengagement therefrom.

United States Patent [191 Jansen June 28, 1974 MACHINE FOR BENDING SHEET STOCK [75] Inventor: Herbert Jansen, Rheydt, Germany [73] Assignee: Mannesmann-Meer Aktiengesellschaft, Monchengladbach, Germany [22] Filed: Apr. 11, 1973 [2]] App]. No.: 349,921

[30] Foreign Application Priority Data PE 1 2 3! [52] US. Cl. 72/465, 72/403 [51] Int. Cl B2ld 37/00 [58] Field of Search 72/399, 389, 455, 383,

[56] References Cited UNITED STATES PATENTS 2,483,00l 9/1949 Carswell 72/399 2,59l,085 4/1952 McCall 72/399 2,796,909 6/1957 Wells 72/399 2,882,954 4/1959 Machian 72/383 3,353,397 1 l/l967 Hoffmann 72/465 FOREIGN PATENTS OR APPLlCATlONS 1,024,32l 3/l953 France 72/389 Primary Examiner-Charles W. Lanham Assistant Examiner-M. J. Keenan Attorney, Agent, or Firm-Ralf H. Siegemund [5 7] ABSTRACT A machine for bending metal sheet or plate stock into a blank of U-shaped cross section, having a plurality of frames which are closed at the top and are disposed along a line in relation to which the stock is to be bent, each frame comprising an upper frame and a lower frame, there being sheet bending members in the lower frame and hydraulic press means with bending punch; each of said upper frames having a pair of tension and tie bar members, hinged individually with their respective lower ends to the lower frame and being inclined towards each other for positions of their upper ends in close proximity to each other; each upper frame further including a horizontally extending cross tie hinged to the said bars close to but not at their said upper ends, the hydraulic means including a press cylinder, being mounted to said cross tie; and resiliently yielding hinge means at the said upper ends of said bar members for interconnecting bar members and hingedly connecting them to each other. The hinge means comprising a pair of bearing segments respectively connected to the upper ends of the bar members, a cylindrical hinge pin engaged by the segments; and tie rod means for resiliently urging the segments into engagement with the pm but permitting partial disengagement therefrom.

8 Claims, 3 Drawing Figures MACHINE FOR BENDING SHEET STOCK BACKGROUND OF THE INVENTION The present invention relates to a machine for bending metal blanks, particularly of the type used in tube and pipe manufacturing plants, wherein sheet metal plates are formed into a blank with U-shaped cross section. The invention relates particularly to improvements of a sheet bending machine having plural closed upright frames arranged along a longitudinal direction and being interconnected. The frames each have an upper and a lower frame, whereby the upper frame supports a hydraulic press cylinder operating a mandrel or punch, while forming members such as rollers are supported in the lower frames. These elements coact as die members for U-ing a blank. A machine of this variety and to be improved by the present invention, is shown, for example, in US. Pat. No. 2,591,085.

The frames as shown in that patent are of uniform, single piece, welded construction. Newer machines for bending sheets separate upper and lower frames, each still being of welded construction, but the two frame parts are bolted together. This known, two part frame construction is still quite expensive to make and requires special machine tools which are expensive in themselves, and the welding construction per se in each instance is still quite expensive.

On the other hand, it has to be observed that pipes and tubes are manufactured with ever increasing diameter, and correspondingly increasing pipe wall thicknesses. The sheet stock bending and forming machines are to be made of larger size accordingly. As a consequence, large machines constructed in accordance with prior art practice have to take up very large bending stress. The welded frame must be of considerable cross section in order to exhibit the required stiffness. On the other hand, it is undesirable to increase the dimensions of such a machine proportionally, and the machines should not become too heavy, because otherwise transport and installation of such a machine becomes too troublesome. I

In order to maintain reasonably low weight of such a forming and bending machine, light construction parts with correspondingly increasing number of weldings have been employed, but because of the welding these machines are more expensive on that account.

SUMMARY OF THE INVENTION It is an object of the present invention to provide for a novel construction of the frames in a sheet bending machine. It is another object of the present invention to provide for a frame construction in a sheet bending machine which optimizes its bending load take-up capability, and particularly, bending stress in the upper frame part, is to be avoided. Also, the machine to be constructed in accordance with the present invention is to avoid as much as possible large welded parts and construction, so as to permit more economical transport and installation.

In accordance with the preferred embodiment of the invention, the frames in such a sheet bending machine each are constructed as upper and lower frames, whereby the upper frame is comprised of two tension rods, struts or tie bars disposed in inclined position towards each other and they are articulated or hinged to the lower frame. The upper ends of the tension rods or tie bars are interconnected by a cross tie, each bar being hingedly connected thereto. These rods extend beyond the hinge points with the cross tie, and the extensions are hingedly and resiliently, yieldingly interconnected. The punch operating cylinder is hinged to the cross tie; the upper ends of these tension rod and bar members are positioned rather closely at the apex of a triangle, whose base is established by the hinges to the lower frame.

As a consequence, each frame consists of four basic parts. The lower frame, the two tension rods tie bars and a cross tie. These elements are of more convenient proportions for transport and installation, even in case of a large machine. Also, each of these parts is not too heavy and can be handled more easily. That, however, is not the only advantage. The utilization and arrangement of tie bar members renders the upper frame substantially free from bending forces; these bar members may have small cross sections accordingly. Actually, they can be constructed from two or more metal sheets placed side by side and interconnected by spacing and connecting elements. The principle tension in the machine during press working is exerted upon the lower frame, which can be constructed accordingly without posing any problems as to excessive weight and dimensions. The lower frame part is usually anchored to a foundation which thereby becomes part of the overall frame and support construction of the machine.

The cross tie will experience some bending force, but again, that poses no problems, as the cross tie is relatively short due to the inclined disposition of the tension rods and the bars. As a consequence of that shortness taken in conjunction with the hinge connection of the several parts, the press force of the cylinder is readily reacted into the tie bars and into the cross tie to act as tension forces therein in each instance.

From a different point of view, the principle of the invention can be seen in the combination of a triangular frame with a trapezoidal frame, whereby triangle and trapezoid are acting (or are acted upon) in sequence. The triangular, hinged frame may suffice by itself, and its principle function is to ensure stability of the upper frame construction as a whole. However, a triangular hinged frame would require reacting the press force into the apex hinge point, which could be an exceedingly impractical feature, and the punch would lack adequate guiding and could readily buckle during press working. Thus, an exclusively triangular hinged frame could pose problems under load. A quadrilateral, hinged frame by itself could assume position and configuration under load so that the tie bars are indeed under tension only. However, an exclusively trapezoidal frame is not stabil under no-load conditions.

The invention combines the advantageous features of both types of frames while avoiding their individual disadvantages, as a result of the combination. The trapezoidal configuration comes into play under load, while under no load conditions the frame stabilizes because of structural super positioning of a hinged triangle. It is important, however, to construct the apex hinge of the triangle so that the trapezoidal portion remains capable of hinge action. The resilient yielding of that apex hinge as suggested provides that feature.

In accordance with a more particular feature of the invention, the hinge in the apex of the construction is established at the upper, extended ends of the two tension rods in that bearing segments (of a segmented bearing bushing) bear against a cylindrical pin from opposite sides, and they are urged against that pin by at least one tie rod. The tie rod is of yielding configuration, and play between the bearing segments as well as clearance of the tie rod as received in bores in the end portions of the tension rods, together provide sufficient yield upon displacements of parts in the frame under load, i.e., during sheet forming. The configuration of the support surfaces as between the tie rod heads and the ends of the tension rods or tie bars adds to the permissible play in the apex hinge point of the frame construction. The resilient yielding of this apex joint and hinge point may be provided by the resiliency of the tie rod itself or a spring may be provided in addition.

DESCRIPTION OF THE DRAWINGS While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which:

FIG. 1 is a front elevation of a sheet bending machine improved in accordance with the preferred embodiment of the invention;

FIG. 2 is a side elevation of the machine shown in FIG. 1; and

FIG. 3 shows a detail in the upper frame portion of the machine of FIGS. 1 and 2.

Proceeding now to the detailed description of the drawings, reference is made first primarily to FIG. 1, as it shows best the salient machine parts as a whole, as well as the novel frame construction. The longitudinal organization of the machine is shown more fully in FIG. 2.

The machine has plural upright frames such as F, Fa, Fb, each having a lower frame 1 and a three-part upper frame. These three parts in each frame are two tie bars 2 and 3, and a cross tie 4 for frame F. Corresponding parts in the other frames have index a and b accordingly.

The two tie bars and tension rod members 2 and 3 are respectively hinged to lower frame 1 by means of pins 11 and 12. Close to (but not right at) their upper ends, bar members 2 and 3 are hinged to cross tie 4 by means of hinge pins 27 and 28. As such, these elements establish a trapezoidal quadrilateral. Another joint between tie bars 2 and 3 is established at their ends as projecting beyond the hinge pins 27 and 28, towards a triganle apex.

A resilient, yielding hinge is established at the apex of the triangle whose base is established by hinges 11 and 12. A pin 13 connects the uppermost portions of bar members 2 and 3 in that these end portions are urged against pin 13 by a tie rod 16. Details of this hinge and joint construction for the triangle apex will be described later with reference to FIG. 3.

A hydraulic press cylinder 30 is connected to cross tie 4, and the piston therein connects to a punch 5. A mandrel or punch bulb 29 connects to punch 5. The punch extends actually over the entire machine and thus connects to plural pistons respectively in the several frames (FIG. 2).

The forming members proper are disposed in the lower frames 1. They include a central die member 6 and lateral sheet forming and bending rollers 7. Rollers 7 are journalled on displaceable, laterally disposed tables or girders 9 and 10. Each table is independently displaceable by means of operating cylinders 8, which are operated independently from press cylinder 30.

Each table or girder 9, 10, is connected by means of a linking arm to a shaft 31. There is one such shaft on each side of the work area. A table 33 is provided for lifting and lowering, and this table carries a set of transport and conveyor rolls 34 for moving the sheet blank into the machine and for removing the resulting U-ed blank from the machine.

After the press punch 29 has been lowered for the sheet bending operation, the tables or girders 9 and 10 are moved particularly towards each other. There are corresponding carrier elements for forming rollers in the said US. Pat. No. 2,591,085, but their movement is controlled in dependence upon operation of the press cylinder. Presently, these support girders 9 and 10 are moved under control of cylinders 8, whose operation is not directly linked to the hydraulic press. The cylinders and hydraulic drives 8 are hydraulically synchronized so that girders or tables 9 and 10 move in unison. It was found that the bending and U-forming process can be controlled better in that manner, and the quality of the U-ed blank is quite high. This property is of advantage if the U-ed blank is subsequently made into a pipe of large diameter as any deficiency in the U-contour has to be eliminated in that subsequent working for obtaining a sufficiently circular pipe.

As stated, the several frames as of FIG. 2 differ as to their identification by index letters a and b. Accordingly, the lower frames 1, la, lb, are interconnected twice; once through the common foundation 35 and additionally via I-beams 38. Analogously, the cross tie 4 of the first upper frame is connected to cross ties 4a and 4b of the other frames by means of I-beams 36 which, in turn, carry a foot bridge or cat walk 37 (see particularly FIG. 2). For completion of the description, it should be noted that FIG. 2 shows also the tie bars 2a and 2b of the second and of the third frame.

The tie bars 2 (and 2a, 2b) as well as the corresponding tie bars 3 etc., each are comprised of sheets 23 and 24 facing each other and being interconnected by spacing and connecting elements 25. In case the tie bars have to take up very high tension forces, one could use three or more sheets per tie bar and they are analogously interconnected.

Turning now to the interconnect construction in the apex of the triangle above the traverse 4 establishing the upper, short side of the trapezoidal quadrilateral as formed by the inclinedly positioned elements 2 and 3, reference is made to FIG. 3. The hinged joint is established primarily by the pin 13, and the upper extensions of bars 2 and 3 are respectively provided with bearing segments 14 and 15 receiving pin 13 in-between. A tie rod 16 urges the bearing segments into engagement with the pin.

The tie rod is spring biased by means of a spring 22, the bias being adjustable by means of nut 26. The tie rod is received in two, generally axially aligned bores in end pieces 18 and 19 respectively of tension bars 2 and 3. The tie rod 16 is held in these bores by means of heads 20 and 21, having curved faces with which to engage the end pieces 18 and 19. The play between bearing elements 14 and 15 in relation to each other as well as the gap and clearance between tie rod 16 in bores 17 on account of a rather loose fit, and the contour of the engaging faces of heads 20 and 21 all determine the extent of mutual displacement of the frame parts in the apex area on account of movements of these parts during a sheet bending operation. FIG. 3 shows, of course, also the cross tie 4 as hingedly connected to frame bars 2 and 3, respectively, by means of the pins 27, 28.

During operation, press force is provided as indicated by arrow P. Due to symmetry in the arrangement, reaction forces P/2 act on each of the hinge pins 27 and 28. That reaction force can be split into two components in each hinge connection. There are first horizontal tension components P4, which act oppositely equal on the cross tie 4, acting therein as tension force accordingly. The second components (P2 on pin 27 P3 on pin 28) run into the bars 2 and 3 as upwardly directed tension producing forces, acting in the direction of the respective tie and tension bars 23.

As a consequence, tension bars 2 and 3 are subjected to longitudinal, tension expansion as between pins ll, 12, on one hand and pins 27, 28 on the other hand. The upper extension of each bar, above the respective pin (27, 28) is not subject to that expansion. However, expansion of the bars 2 and 3, which is, of course, rather small to begin with, modifies somewhat the angle of inclination or top apex angle of the bars to each other. As a consequence, the uppermost hinge at pin 13- bearing l4, 15, opens to a slight degree. This, however, has no influence on the suspension of the press force producing cylinder 30 whose action produces all these results. Moreover, the force lines P2 P3 when extended intersect in the center of hinge pin 13.

It can thus be seen that under press action load, the frame acts as trapezoidal support, with no or very little bending in its bars and ties. The main bending action in the frame occurs in lower frame 1.

Under no load conditions, the upper hinge construction establishes a position stabilizing triangle apex point, and avoids any instability of and in the quadrilateral as set up by elements 1 l, 12, 27, 28, which instability would occur under no load conditions in the absence of the triangle completing construction. One can also say that the triangle stabilizes the trapezoid under no load conditions.

As far as installation is concerned, the lower frame has configuration of a sideways positioned C, which is open in upward direction. Accordingly, that part can readily be installed first, and inserts and machine parts to be received can be mounted prior to erecting the upper frames. The sheet construction of the tension and tie bar members 2 and 3 permits assembly at location, if the connecting elements include bolts. The upper frame is then completed on location by hingedly interconnecting the parts 2, 3 and 4 and by hinging the parts 2 and 3 to the lower frame 1.

The invention is not limited to the embodiments described above but all changes and modifications thereof not constituting departures from the spirit and scope of the invention are intended to be included.

I claim:

1. In a machine for bending metal sheet or plate stock into a blank of U-shaped cross section, having a plurality of frames which are closed at the top and being disposed along a line in relation to which the stock is to be bent, each frame comprising an upper frame and a lower frame, there being sheet bending members in the lower frame and hydraulic press means with bending punch the improvement comprising:

each said upper frames having a pair of tension and tie bar members, hinged individually with their respective lower ends to the lower frame and being inclined towards each other for positions of their upper ends in close proximity to each other;

each upper frame further including a horizontally extending cross tie hinged to the said bars close to but not at their said upper ends, the hydraulic means including a press cylinder being mounted to said cross tie; and

resiliently yielding hinge means at the said upper ends of said bar members for interconnecting bar members and hingedly connecting them to each other.

2. In a machine as in claim 1, said hinge means comprising a pair of bearing segments respectively connected to the upper ends of the bar members; a cylindrical hinge pin engaged by the segments; and tie rod means for resiliently urging the segments into engagement with the pin but permitting partial disengagement therefrom.

3. In a machine as in claim 2, the tie rod means including a tie rod with heads, there being aligned bores in the bar members for receiving the tie rod, the heads coacting with the bar members through curved surfaces.

4. In a machine as in claim 3, the tie rods being spring biased.

5. In a machine as in claim 1, the lower frame constructed with a sideways positioned C-shaped cross section.

6. In a machine as in claim 1, the bending members including a pair of rollers disposed for individually controlled displacement towards each other.

7. In a machine as in claim 1, the bar members each being comprised of a plurality of elongated sheets placed side by side but at a distance from each other and being interconnected by spacing and connecting elements.

8. In a machine as in claim 1, there being a pair of hinge pins for connecting the bar members to the cross tie, bar members having normal disposition so that lines running in the same directions as the directions of extension of the bar members, and traversing the center of the respective hinge pins of the pair intersect at least approximately in the center of said hinge pair of the hinge means. 

1. In a machine for bending metal sheet or plate stock into a blank of U-shaped cross section, having a plurality of frames which are closed at the top and being disposed along a line in relation to which the stock is to be bent, each frame comprising an upper frame and a lower frame, there being sheet bending members in the lower frame and hydraulic press means with bending punch the improvement comprising: each said upper frames having a pair of tension and tie bar members, hinged individually with their respective lower ends to the lower frame and being inclined towards each other for positions of their upper ends in close proximity to each other; each upper frame further including a horizontally extending cross tie hinged to the said bars close to but not at their said upper ends, the hydraulic means including a press cylinder being mounted to said cross tie; and resiliently yielding hinge means at the said upper ends of said bar members for interconnecting bar members and hingedly connecting them to each other.
 2. In a machine as in claim 1, said hinge means comprising a pair of bearing segments respectively connected to the upPer ends of the bar members; a cylindrical hinge pin engaged by the segments; and tie rod means for resiliently urging the segments into engagement with the pin but permitting partial disengagement therefrom.
 3. In a machine as in claim 2, the tie rod means including a tie rod with heads, there being aligned bores in the bar members for receiving the tie rod, the heads coacting with the bar members through curved surfaces.
 4. In a machine as in claim 3, the tie rods being spring biased.
 5. In a machine as in claim 1, the lower frame constructed with a sideways positioned C-shaped cross section.
 6. In a machine as in claim 1, the bending members including a pair of rollers disposed for individually controlled displacement towards each other.
 7. In a machine as in claim 1, the bar members each being comprised of a plurality of elongated sheets placed side by side but at a distance from each other and being interconnected by spacing and connecting elements.
 8. In a machine as in claim 1, there being a pair of hinge pins for connecting the bar members to the cross tie, bar members having normal disposition so that lines running in the same directions as the directions of extension of the bar members, and traversing the center of the respective hinge pins of the pair intersect at least approximately in the center of said hinge pair of the hinge means. 